Reduced cerebral blood flow of lingual gyrus associated with both cognitive impairment and gait disturbance in patients with idiopathic normal pressure hydrocephalus

Analysis of dynamic network reconfiguration in HIV patients with cognitive impairment based multilayer network

Approximately half of HIV patients continue to experience HIV-associated neurocognitive disorders (HAND). Our study aims to evaluate changes in the dynamic activity patterns of functional brain communities in the early stages of HIV infection by comparing time-varying multilayer network metrics. A total of 165 persons living with HIV but without neurocognitive disorders (PWND), 173 individuals with asymptomatic neurocognitive impairment (ANI), and 100 matched healthy controls (HC) were enrolled. A time-varying multilayer network model was constructed, and global modularity (Q value) and nodal flexibility were calculated using different parameter settings (γ = [0.9, 1, 1.1], ω = [0.5, 0.75, 1]). Brain functional alterations in the PWND and ANI groups were evaluated from both global and nodal perspectives. Associations between network measures, clinical variables, and cognitive performance were also explored. Using the full connectivity matrix, no significant differences in global modularity (Q value) were found among the three groups. However, when thresholding the matrix to retain the top 10% of strongest connections, the ANI group showed significantly lower modularity than the HC group across all γ and ω combinations (p < 0.05). At γ = 0.9 and ω = 0.5, reduced nodal flexibility was observed in visual network regions in the PWND group, while the ANI group showed reduced flexibility in regions belonging to the default mode network (DMN), sensorimotor network (SMN), and limbic network (LIM). At γ = 0.9 and ω = 1, the ANI group exhibited increased flexibility in DMN regions compared to HC. Additionally, thresholding the top 10% connections revealed increased flexibility in the right lingual gyrus (visual network) in ANI compared to HC (FDR corrected, p < 0.05). Nodal flexibility was positively correlated with neurocognitive performance in the PWND group, whereas a significant negative correlation was observed in the ANI group. Regardless of cognitive impairment, HIV patients exhibit abnormalities in dynamic community structures. These findings provide new insights and perspectives for the early detection of brain damage, advancing our current understanding of time-varying multilayer networks in HIV patients.

Association of immune-mediated diseases with the risk of dementia and brain structure in UK Biobank participants

BACKGROUND

Immunity and inflammation may be essential to the pathogenesis of dementia. However, the association of immune-mediated diseases with the risk of incident dementia has not been well characterised.

OBJECTIVES

We aimed to investigate the prospective association of 27 immune-mediated diseases and incident dementia risk and to explore the underlying mechanisms driven by brain structures.

METHODS

We included 487 459 UK Biobank participants aged 37-73 years without dementia at enrolment. Immune-mediated diseases and dementia cases were ascertained according to the International Classification of Diseases codes. Time-varying Cox proportional hazards regression and general linear regression models were used to examine the association of immune-mediated disease with incident dementia risk and brain morphometric measures, respectively.

RESULTS

Over a median follow-up of 12.3 years, 1654 cases of incident dementia were documented in 86 243 patients with immune-mediated diseases. Overall, immune-mediated diseases were associated with a higher all-cause dementia risk (hazard ratio [HR], 1.24; 95% confidence interval, 1.17-1.32). Five out of 27 immune-mediated diseases were associated with an increased risk of dementia individually. Comorbidity of multiple immune-mediated diseases further increased the risk. Moreover, the immune-mediated disease was associated with smaller total surface areas of both left (β, -286.51; SE, 102.58; P = .014) and right hemispheres (β, -298.56; SE, 103.96; P = .016), greater white matter hyperintensities volume (β, 1.02; SE, 0.13; P < .001) and less healthy white matter microstructures.

CONCLUSIONS

Immune-mediated diseases were associated with an increased risk of incident dementia, and the association of those diseases with brain structural abnormalities might provide clues to the underlying mechanisms.

Local Neuronal Activity and the Hippocampal Functional Network Can Predict the Recovery of Consciousness in Individuals With Acute Disorders of Consciousness Caused by Neurological Injury

AIMS

There is limited research on predicting the recovery of consciousness in patients with acute disorders of consciousness (aDOC). The purpose of this study is to investigate the altered characteristics of the local neuronal activity indicated by the amplitude of low-frequency fluctuations (ALFF) and functional connectivity (FC) of the hippocampus network in patients with aDOC caused by neurological injury and to explore whether these characteristics can predict the recovery of consciousness.

METHODS

Thirty-seven patients with aDOC were included, all of whom completed resting-state functional magnetic resonance imaging (rsfMRI) scans. The patients were divided into two groups based on prognosis of consciousness recovery, 24 patients were in prolonged disorders of consciousness (pDOC) and 13 in emergence from minimally conscious state (eMCS) at 3 months after neurological injury. Univariable and multivariate logistic regression analyses were used to investigate the clinical indicators affecting patients' recovery of consciousness. The ALFF values and FC of the hippocampal network were compared between patients with pDOC and those with eMCS. Additionally, we employed the support vector machine (SVM) method to construct a predictive model for prognosis of consciousness based on the ALFF and FC values of the aforementioned differential brain regions. The accuracy (ACC), area under the curve (AUC), sensitivity, and specificity were used to evaluate the efficacy of the model.

RESULTS

The FOUR score at onset and the length of mechanical ventilation (MV) were found to be significant influential factors for patients who recovered to eMCS at 3 months after onset. Patients who improved to eMCS showed significantly increased ALFF values in the right calcarine gyrus, left lingual gyrus, right middle temporal gyrus, and right precuneus compared to patients in a state of pDOC. Furthermore, significant increases in FC values of the hippocampal network were observed in the eMCS group, primarily involving the right lingual gyrus and bilateral precuneus, compared to the pDOC group. The predictive model constructed using ALFF alone or ALFF combined with FC values from the aforementioned brain regions demonstrated high accuracies of 83.78% and 81.08%, respectively, with AUCs of 95% and 94%, sensitivities of 0.92 for both models, and specificities of 0.92 for both models in predicting the recovery of consciousness in patients with aDOC.

CONCLUSION

The present findings demonstrate significant differences in the local ALFF and FC values of the hippocampus network between different prognostic groups of patients with aDOC. The constructed predictive model, which incorporates ALFF and FC values, has the potential to provide valuable insights for clinical decision-making and identifying potential targets for early intervention.

Cortical networks of parkinsonian gait: a metabolic and functional connectivity study

OBJECTIVE

Locomotion is an automated voluntary movement sustained by coordinated neural synchronization across a distributed brain network. The cerebral cortex is central for adapting the locomotion pattern to the environment and alterations of cortical network dynamics can lead to gait impairments. Gait problems are a common symptom with a still unclear pathophysiology and represent an unmet therapeutical need in Parkinson's disease. Little is known about the cortical network dynamics of locomotor control in these patients.

METHODS

We studied the cortical basis of parkinsonian gait by combining metabolic brain imaging with high-density EEG recordings and kinematic measurements performed at rest and during unperturbed overground walking.

RESULTS

We found significant changes in functional connectivity between frontal, sensorimotor, and visuomotor cortical areas during walking as compared to resting. Specifically, hypokinetic gait was associated with poor information flow from the supplementary motor area (SMA) to precuneus and from calcarine to lingual gyrus, as well as high information flow from calcarine to cuneus.

INTERPRETATION

Our findings support a role for visuomotor integration processes in PD-related hypokinetic gait and suggest that reinforcing visual information may act as a compensatory strategy to allow SMA-mediated feedforward locomotor control in PD.

Differences of individual gray matter networks between MCI patients who converted to AD within 3 Years and nonconverters

Objective

Here we aimed to explore the differences in individual gray matter (GM) networks at baseline in mild cognitive impairment patients who converted to Alzheimer's disease (AD) within 3 years (MCI-C) and nonconverters (MCI-NC).

Materials and methods

Data from 461 MCI patients (180 MCI-C and 281 MCI-NC) were obtained from the Alzheimer's Disease Neuroimaging Initiative (ADNI). For each subject, a GM network was constructed using 3D-T1 imaging and the Kullback-Leibler divergence method. Gradient and topological analyses of individual GM networks were performed, and partial correlations were calculated to evaluate relationships among network properties, cognitive function, and apolipoprotein E (APOE) €4 alleles. Subsequently, a support vector machine (SVM) model was constructed to discriminate the MCI-C and MCI-NC patients at baseline.

Results

The gradient analysis revealed that the principal gradient score distribution was more compressed in the MCI-C group than in the MCI-NC group, with scores for the left lingual gyrus, right fusiform gyrus and left middle temporal gyrus being increased in the MCI-C group (p < 0.05, FDR corrected). The topological analysis showed significant differences in nodal efficiency in four nodes between the two groups. Furthermore, the regional gradient scores or nodal efficiency were found to be significantly related to the neuropsychological test scores, and the left middle temporal gyrus gradient scores were positively associated with the number of APOE €4 alleles (r = 0.192, p = 0.002). Ultimately, the SVM model achieved a balanced accuracy of 79.4% in classifying MCI-C and MCI-NC patients (p < 0.001).

Conclusion

The whole-brain GM network hierarchy in the MCI-C group was more compressed than that in the MCI-NC group, suggesting more serious cognitive impairments in the MCI-C group. The left middle temporal gyrus gradient scores were related to both cognitive function and APOE €4 alleles, thus serving as potential biomarkers distinguishing MCI-C from MCI-NC at baseline.

Cognitive function and brain activation before and after transcutaneous cervical vagus nerve stimulation in healthy adults: A concurrent tcVNS-fMRI study

Transcutaneous vagus nerve stimulation, which involves the application of electrical currents to the cervical (tcVNS) or auricular (taVNS) branches of the vagus nerve, may be a potential treatment for improving cognitive dysfunction. taVNS may improve cognitive performance in healthy adults, and fewer studies have been performed on the effects of tcVNS on cognition in healthy subjects. We conducted a randomized, single-blind, crossover-controlled trial to investigate the effects of tcVNS stimulation on cognitive function and neural activity in the brains of healthy adults. This study provides support for further tcVNS studies for the treatment of cognitive impairment. Twenty-one participants were randomly divided into two groups, A and B. Group A received tcVNS first and then sham-tcVNS, while group B received the intervention in the reverse order, receiving sham stimulation first and then true stimulation. All subjects were required to perform cognitive function tests before and after receiving intervention, and functional magnetic resonance imaging (fMRI) was performed concurrently during the intervention. We hypothesized that tcVNS would have an effect on the cognitive performance of the subjects and alter the neural activity of the brain. The present study showed that tcVNS had beneficial effects on cognitive performance, mainly improving memory and language skills and attention. tcVNS intervention produced significant spontaneous neural activity in the calcarine gyrus, fusiform gyrus, lingual gyrus, and parahippocampal gyrus of the brain. Future tcVNS/fMRI trials will need to explore the effects of changes in stimulus parameters on the neural activity response of the brain.

TRPV4 mRNA is elevated in the caudate nucleus with NPH but not in Alzheimer's disease

Symptoms of normal pressure hydrocephalus (NPH) and Alzheimer's disease (AD) are somewhat similar, and it is common to misdiagnose these two conditions. Although there are fluid markers detectable in humans with NPH and AD, determining which biomarker is optimal in representing genetic characteristics consistent throughout species is poorly understood. Here, we hypothesize that NPH can be differentiated from AD with mRNA biomarkers of unvaried proximity to telomeres. We examined human caudate nucleus tissue samples for the expression of transient receptor potential cation channel subfamily V member 4 (TRPV4) and amyloid precursor protein (APP). Using the genome data viewer, we analyzed the mutability of TRPV4 and other genes in mice, rats, and humans through matching nucleotides of six genes of interest and one house keeping gene with two factors associated with high mutation rate: 1) proximity to telomeres or 2) high adenine and thymine (A + T) content. We found that TRPV4 and microtubule associated protein tau (MAPT) mRNA were elevated in NPH. In AD, mRNA expression of TRPV4 was unaltered unlike APP and other genes. In mice, rats, and humans, the nucleotide size of TRPV4 did not vary, while in other genes, the sizes were inconsistent. Proximity to telomeres in TRPV4 was <50 Mb across species. Our analyses reveal that TRPV4 gene size and mutability are conserved across three species, suggesting that TRPV4 can be a potential link in the pathophysiology of chronic hydrocephalus in aged humans (>65 years) and laboratory rodents at comparable ages.